A blind rivet comprises a hollow rivet body formed at one end with a head and having a pin or mandrel extending longitudinally through the rivet and protruding from the head end. The mandrel is fitted into a riveting tool such that the head lies against an abutment on the tool. Actuation of the tool pulls the mandrel back through the rivet and upsets this rivet. The mandrel is sufficiently strong to upset the rivet but not pull all the way through it so that once a predetermined resistance has been met the mandrel breaks off, leaving the upset rivet and end of the mandrel together in the workpiece with the broken-off end of the mandrel still held in the tool.
When such a tool is used with rivets of aluminum or steel a relatively short stroke is all that is necessary to upset the rivet. In order properly to deform the rivet a relatively great force is needed so that the tool works with a considerable mechanical advantage. Thus a relatively wide displacement of the handles gives a relatively small displacement at the holding end of the tool.
Synthetic-resin rivets, frequently made of a rigid polyamide such as nylon, require a much greater working stroke to be properly upset. Thus when such rivets are set with a conventional blind-riveting tool it is often necessary to actuate the handle several times before the mandrel snaps off and the rivet is properly upset. Even a pneumatic or pneumatic-hydraulic blind riveting tool must be actuated several times to upset such rivets.